If you are still using a Windows Phone device, you have very limited options:
If you own a Lumia 950/950 XL, you can install Windows 10 on ARM, which allows running the Android APK version of WhatsApp via a subsystem. This is complex and unstable. whatsapp xap download link
Now that we've covered the basics, let's get to the good stuff – downloading and installing WhatsApp XAP using the XAP download link. Here's a step-by-step guide: If you are still using a Windows Phone
By following the guide and taking necessary precautions, you can experience WhatsApp XAP and its features. However, if you're unsure or uncomfortable with the process, it's always recommended to stick with the official WhatsApp application for a safe and seamless experience. Here's a step-by-step guide: By following the guide
refers to the file format used for applications on the older Windows Phone Windows 10 Mobile
Historically, these could be "sideloaded" using an SD card or a PC with the Windows Phone SDK.